I love this idea too though. I'm guessing pressure is one of the least effected by being inside or in a pocket, while still being highly useful for weather prediction.
Longer term, I can see these sensors being embedded in glasses or contacts, which could be an easier problem.
I believe the data in aggregate will provide a pretty good map of the pressure gradient which could then be fixed to the more accurate dedicated weather stations. Think of it like the 10,000 year clock which uses a clock known to drift in conjunction with a solar time fix to calibrate.